Such filters are known and are, for example, connected in the output switching circuits of power amplifiers operating on centimeter waves in order to reduce the rate of harmonic radiation in space.
The known filters consist of a rectangular primary waveguide the four sides or at least one of the two broad sides whereof are attached to lateral guides which are also rectangular but have a smaller cross section than the primary guide. The two openings of these filters are sometimes provided with a taper or a stepped impedance matching means; such impedance matching means, which forms a rectangular guide-to-rectangular guide coupler, is intended to boost the coupling of the lateral guides by reducing the distance between the two broad sides of the main guide, which is to say, by providing an internal cross section for the main guide the small sides whereof are smaller than those of the filter openings (inlets and outlets); the broad sides on the other hand are given the same dimensions as the broad sides of the outside rectangular guides to which the filter is coupled.
These prior art filters are costly due to the large number of lateral guides which must generally be associated with the primary guide. Moreover, they are very difficult to manufacture using electroerosion or electroforming techniques.
It is the object of this invention to obviate, or at least abate these disadvantages.